The apical dominance refers to the phenomenon that the terminal bud is long and the lateral bud is restrained on one branch. Generation principle: the auxin formed by the terminal bud is transported downward, which increases the concentration of auxin near the lateral bud and is inhibited because the lateral bud is sensitive to auxin; At the same time, the top with high auxin content took away the nutrition of the lateral buds, resulting in insufficient nutrition of the lateral buds. It can be seen that the top advantage is beneficial for plants to grow taller, and the top advantage principle is widely used in fruit tree pruning. Artificial removal of terminal buds can promote the production of lateral buds and increase the number of branches. In production practice, pruning of fruit trees, topping of tea trees and topping of cotton are often carried out according to the principle of topping advantage, so as to increase branches and increase yield. It can be seen that A is correct.

So choose: a.